1. Field of the Invention
The present invention relates to fabrication methods of package structures, and, more particularly, to a fabrication method of a package structure having MEMS (micro-electro-mechanical system) elements.
2. Description of Related Art
MEMS elements have integrated electrical and mechanical functions and can be fabricated through various micro-fabrication technologies. A MEMS element can be disposed on a substrate and covered by a shield or packaged with an underfill adhesive so as to protect against damage caused by the external environment.
FIG. 1 shows a cross-sectional view of a conventional package structure having a MEMS element. Referring to FIG. 1, a MEMS element 11, such as a pressure-sensing element, is disposed on an LGA (land grid array) substrate 10 and conductive pads 111 of the MEMS element 11 are electrically connected to conductive pads 101 of the LGA substrate 10 through a plurality of bonding wires. Further, a metal lid 12 is disposed on the substrate 10 for covering the MEMS element 11 so as to protect the MEMS element 11 against external damage and pollution. However, such a package structure has a large size and cannot meet the demand for lighter, thinner and smaller electronic products.
Accordingly, FIG. 2 shows a wafer-level package structure as disclosed by US Patent Application No. 2006/0185429. Referring to FIG. 2, a plurality of MEMS elements 21, such as pressure-sensing elements, are directly formed on a silicon substrate 23, and glass lids 24 are attached to the MEMS elements 11 through anodic bonding.
Further, the silicon substrate 23 has sensing cavities 231 and through holes 232 formed therein by using TSV (through silicon via) technology. Such TSV technology uses KOH as an etchant for forming the through holes or recesses.
Compared with the previously described package structure, the present package structure has a greatly reduced size. However, the TSV technology for forming the through holes and recesses is costly and requires a high degree of accuracy, thus complicating the fabrication process and increasing the fabrication cost.
Therefore, it is imperative to overcome the above-described drawbacks of the prior art.